1. Field of the Invention
The present invention relates to an adhesion enhancer used for enhancing adhesion between a primer and a polymer composition substrate, and a polymer composition containing the adhesion enhancer. More specifically, the present invention relates to an adhesion enhancer and a polymer composition containing the adhesion enhancer, which can be added to the polymer composition so as to enhance adhesion of polymer composition substrates obtained from the polymer composition to a primer applied to increase the adhesion performance of the substrates prior to applying an adhesive in combining the substrates together.
2. Description of the Related Art
Generally, there are two methods of joining a plurality of substrates obtained from a polymer composition; 1) using an adhesive alone to join the substrates into a polymer substrate/adhesive/polymer substrate sandwich and 2) using both a primer and an adhesive to get a polymer substrate/primer/adhesive/primer/polymer substrate sandwich.
Specifically, the second method involves preparing polymer composition substrates coated with a primer, which is capable of coupling with the polymer composition substrates, and then joining the polymer composition substrates using an adhesive.
There are several methods of increasing adhesion between the adhesive and the substrates obtained from the polymer composition—promoting the adhesion performance of the adhesive, or improving the performance of adhesion-related materials such as the primer, or the like.
The methods most widely used in the footwear industry are surface-processing methods for processing the surface of polymer composition substrates to be joined, and a method of adding an adhesion-enhancing material to the polymer composition. These methods are to make the primer well bonded to the polymer composition substrates.
Due to difficulty in joining a plurality of the polymer composition substrates with an adhesive alone, the surface of one polymer composition substrate is coated with a primer and then an adhesive and bonded to the other polymer composition substrates.
To improve the performance of such primers, there have been developed a variety of primer compositions, which achieve good adhesion to a specific polymer composition substrate solely rather than all kinds of polymer composition substrates.
Primers, despite their remarkably improved performance, show a deterioration in adhesion performance to a specific polymer composition substrate, so in many cases the polymer composition substrate is surface-processed before being coated with a primer. In other words, to enhance the adhesion performance of the polymer composition substrate to the primer, the one polymer composition substrate is separately surface-processed in different ways, coated with the primer and then an adhesive, and bonded to the other polymer composition substrates.
The various surface-processing methods for polymer composition substrates may include UV irradiation, corona discharge exposure, acid etching, plasma process, solvent cleaning, polishing process using a polishing compound, or the like. Among these methods, polishing process using a polishing compound and UV irradiation are now most widely used in the footwear industry.
The surface of the polymer composition substrate, surface-modified by the above-mentioned various methods, is enhanced in adhesion to the primer but problematically too unstable for permanent use. Moreover, there is a need to introduce a separate surface-processing line for the polymer composition substrates, resulting in a delay of manufacture, a troublesome need to consider the proceeding/succeeding process, and a resultantly increased burden of cost.
There is also disclosed a method of adding a specific adhesion-enhancing material to the polymer composition, in which method the polymer composition for enhancing adhesion is ready to attach to rolls, leading to actual difficulty of manufacture. Additionally, such an adhesion-enhanced composition as to show a remarkable performance has never so far been made or achieved.